1. Field of the Invention
This invention relates to aqueous pearlescent concentrates containing esters of polybasic carboxylic acids or hydroxycarboxylic acids, emulsifiers and optionally polyols, to a process for their production, to a process for the production of pearlescent surface-active formulations using the concentrates and to the use of esters of polybasic carboxylic acids and hydroxycarboxylic acids as pearlescent waxes.
2. Discussion of Related Art
For centuries, the softly shimmering luster of pearls has held a particular fascination for human beings. It is therefore no wonder that manufacturers of cosmetic preparations endeavour to give their products an attractive, valuable and rich appearance. The first pearlescence used in cosmetics in the middle ages was a pearlescent paste of natural fish scales. At the beginning of the present century, it was discovered that bismuth oxide chlorides were also capable of producing pearlescence. By contrast, pearlescent waxes, particularly of the glycol monofatty acid ester and difatty acid ester type, are of importance in modem cosmetics, being used mainly for the production of pearlescence in hair shampoos and shower gels. An overview of modern pearlescent formulations was published by A. Ansmann and R. Kawa in Parf. Kosm., 75, 578 (1994).
Various formulations capable of providing surface-active products with the required pearlescence are known from the prior art. For example, German patent applications DE-A1 38 43 572 and DE-A1 41 03 551 (Henkel) describe pearlescent concentrates in the form of free-flowing aqueous dispersions containing 15 to 40% by weight of pearlescent components, 5 to 55% by weight of emulsifiers and 0.1 to 5% by weight or 15 to 40% by weight of polyols. The pearlescent waxes are acylated polyalkylene glycols, monoalkanolamides, linear saturated fatty acids or ketosulfones. European patents EP-B1 0 181 773 and EP-B1 0 285 389 (Procter & Gamble) describe shampoo compositions containing surfactants, non-volatile silicones and pearlescence waxes. European patent application EP-A2 0 205 922 (Henkel) relates to free-flowing pearlescent concentrates containing 5 to 15% by weight of acylated polyglycols, 1 to 6% by weight of fatty acid monoethanolamides and 1 to 5% by weight of nonionic emulsifiers. According to the teaching of European patent EP-B1 0 569 843 (Hoechst), nonionic, free-flowing pearlescent dispersions can also be obtained by preparing mixtures of 5 to 30% by weight of acylated polyglycols and 0.1 to 20% by weight of selected nonionic surfactants. In addition, European patent application EP-A2 0 581 193 (Hoechst) describes free-flowing, preservative-free pearlescent dispersions containing acylated polyglycol ethers, betaines, anionic surfactants and glycerol. Finally, European patent application EP-A1 0 684 302 (Th. Goldschmidt) relates to the use of polyglycerol esters as crystallization aids for the production of pearlescent concentrates.
Despite the large number of formulations, there is a constant need on the market for new pearlescent waxes which, in contrast to acylated polyglycols for example, do not contain any ethylene oxide units and which are distinguished from known products by their brilliant luster, even when used in smaller quantities, so that critical ingredients, such as silicones for example, may also be used without any adverse effect on the stability of the formulations and which, at the same time, contain ester groups, thus guaranteeing adequate biodegradability, and which are free-flowing and hence easy to handle, particularly in concentrated form. Accordingly, the problem addressed by the present invention was to provide new pearlescent concentrates which would satisfy the complex requirement profile described above.